The following information is provided to assist the reader to understand the devices, systems, methods and other technology disclosed below and the environment in which they will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the devices, systems methods and other technology disclosed below or the background thereof. The disclosure of all references cited herein are incorporated by reference.
In cases of respiratory failure, carbon dioxide (CO2) removal, rather than oxygen (O2) delivery, is often a primary obstacle in treatment. The therapeutic potential of extracorporeal carbon dioxide removal (ECCO2R) in facilitating lung protective ventilation strategies has been established through partial ECCO2R devices such as the NOVALUNG® interventional lung assist device (a membrane ventilator/extracorporeal artificial lung) available from Novalung GmbH of Heilbronn, Germany and the HEMOLUNG® respiratory assist system (a respiratory assist system/extracorporeal artificial lung) available from ALung Technologies of Pittsburgh, Pa. USA. Such devices, sometimes referred to as artificial lungs, are employed to oxygenate the blood and to remove CO2. Hollow fiber membrane (HFM) based artificial lungs began to replace bubble oxygenators in the 1980s. In that regard, HFM-based artificial lungs exhibit improved gas exchange performance as compared to bubble oxygenators. The first HFM type artificial lung was developed in 1971. However, the performance of early oxygenators was unacceptable as a result of fiber wetting and plasma leak problems.
Composite fibers, constructed with a true membrane layer between microporous walls, are commercially available. Although, the composite fiber had excellent plasma wetting resistance, the permeance of the membrane was insufficient for intravenous oxygenation. Recent advances in membrane technology, however, have enabled the development of noble membranes such as polyolefin-based hollow fiber membrane that exhibit both good gas permeance and high plasma wetting resistance.
Currently available artificial lungs devices typically include bundles of microporous hollow fiber membranes through which oxygen passes while blood is perfused around the fibers. A review of artificial lungs and hollow fiber membrane technology is provided in Federspiel W J, Henchir K A. 2004. Lung, Artificial: Basic principles and current applications. Encyclo Biomat Biomed Eng 910-921, the disclosure of which is incorporated herein by reference. In general, oxygen is transferred from the lumen of the fibers into the blood; while CO2 is transferred from the blood into the lumen of the fibers and is removed from the device. In the current artificial lung model, which is based on passive diffusion, the efficiency of CO2 and O2 gas exchange are limited by the fiber surface area to blood volume ratio. Gas exchange can be improved by increasing this ratio at the cost of increasing the overall size of the artificial lung device. Additionally, CO2 removal rates are limited at lower blood flow rates.